The invention relates to an orthopedic appliance, often referred to as an external fixator, for stabilized maintenance of spaced portions of a bone fracture and for the selective and progressive incremental adjustment thereof in the course of osteosynthesis, i.e., bone healing at the fracture. The invention has particular use in application to small bone fractures, as of the hand or foot.
From German Patent DE-3,701,533 C2 (and its corresponding U.S. Pat. No. 4,988,349), a fixator of the character indicated is known wherein a short central spacer has flexible connection at its respective ends, via twin ball joints, to separate arms which can be so selectively clamped as to provide a wide range of universal angular setting between the two arms, thereby providing a wide range of adjustment for bone-fastener units that anchor bone screws or pins via selectively adjustable fixation of such units to the respective arms. The design permits swivel and height adjustment of the bone-fastener units via individually locked ball joints at the central spacer, thereby creating added freedom of adjustment over a widened overall angular range. Thus, even very complex bone positions and their fine adjustment can be controlled by the surgeon.
When applying an external fixator in the area of the hand and of individual fingers, the surgeon also needs a maximum range of adjustment of single elements in relation to each other. At the same time, however, the structural elements should be kept small enough so that they will interfere to a minimum degree with movements of the hand, for example. The fixator of said patent has serious limitations in such a small-bone context.